First, let me get a political rant out of the way: "Gee, yet another show with a WASPy main cast. Thanks, Hollywood." Rant over.

Now to the real reasons. To begin with, 85 million years ago is a !!!Stupid!!! choice for humans fleeing a dying 22nd century Earth. If the settlers haven't managed to bring along a few cows, horses, pigs, etc., just how do they plan domesticating herbivores that (a) can stand 20 feet at the shoulder and reach 100 feet in length; or (b) are heavily armored all over and Only half the size of a city bus. Meanwhile, of course, they'll be trying to avoid T.Rex, various raptors, etc.

Hopefully, the settlers will have brought a few seed packets of modern grains, etc. along. Otherwise, what are they going to do for food and clothing?

And there's the problem of natural resources and a future industrial base (unless they decide to become cave men). 85 million years ago, there'll be a definite lower available amount of petroleum, natural gas, etc. With major continental shift to come before Earth reaches its present arrangement of land and sea, how will the settlers know where to even look for these resources?

A far better time for the basic show concept would be 40-50,000 years ago, toward the end of the last Ice Age. The continents are mostly where they are now, so you'll know where to find resources when you need them. If you can only bring a few domestic animals and will be heaving depending on frozen embryos, it should be fairly easy to use aurochs, for example, as host mothers to speed up production of dairy cows. Secondly, you'd have not just genetically modern humans around (Cro-Magnon) but another intelligent species still here (Neandertal). Incidentally, if you think the two species never interbred, take a good look at a picture of an elderly Charles Darwin.